1. Technical Field
The present invention relates to polymers. More particularly, the present invention relates to cross-linked copolymers containing polymerized units of one or more quaternary ammonium salt monomers. These polymers are suitable for water treatment applications, specifically removal of heavy metal ions by adsorption.
2. Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Heavy metals are released into the surface and ground water because of various activities such as electroplating, and pigment and paint manufacturing. Because of their toxicity and tendency to bioaccumulate, the removal of metals from industrial effluents before discharge into the environment is required to mitigate any impact on plants, animals and humans [Heidari, A., H. Younesi, and Z. Mehraban, Removal of Ni(II), Cd(II), and Pb(II) from a ternary aqueous solution by amino functionalized mesoporous and nano mesoporous silica. Chemical Engineering Journal, 2009. 153(1-3): p. 70-79 (reference), incorporated herein by reference in its entirety]. Lead is one of the most toxic metals that are widely used in various industries, such as battery and glass manufacturing, metal plating and finishing, printing and tanning. The permissible levels of lead in drinking and waste water are 0.05 mg/L and 0.005 mg/L, respectively [(EPA), E.P.A., Environmental Pollution Control Alternatives. 1990 (EPA/625/5-90/025, EPA/625/4-89/023) (reference), incorporated herein by reference in its entirety]. Several conventional methods are used for the removal of pollutants [Jiang, M.-q., et al., Removal of Pb(II) from aqueous solution using modified and unmodified kaolinite clay. Journal of Hazardous Materials, 2009. 170(1): p. 332-339 (reference), incorporated herein by reference in its entirety]. However, these technologies are either expensive for the treatment and disposal of the secondary toxic sludge or ineffective when the toxic metal is present in wastewaters at low concentrations [Rao, M. M., et al., Removal of some metal ions by activated carbon prepared from Phaseolus aureus hulls. Journal of Hazardous Materials, 2009. 166(2-3): p. 1006-1013 (reference), incorporated herein by reference in its entirety].
Alternatively, heavy metals in wastewater are removed by adsorption which is both efficient and relatively simple. A successful adsorption process depends on the adsorption performance of the adsorbents. Various conventional adsorbents have been reported for the removal of lead from wastewaters including activated carbon, clay, metal oxides nanoparticles and nanomaterials [Ghaedi, M., et al., Comparison of the efficiency of palladium and silver nanoparticles loaded on activated carbon and zinc oxide nanorods loaded on activated carbon as new adsorbents for removal of Congo red from aqueous solution: Kinetic and isotherm study. Materials Science and Engineering: C, 2012. 32(4): p. 725-734; Dias, J. M., et al., Waste materials for activated carbon preparation and its use in aqueous-phase treatment: A review. Journal of Environmental Management, 2007. 85(4): p. 833-846; Erdem, E., N. Karapinar, and R. Donat, The removal of heavy metal cations by natural zeolites. Journal of Colloid and Interface Science, 2004. 280(2): p. 309-314 (references), each incorporated herein by reference in their entirety”. However, small particle size of nanoparticle results in the difficulty of separation from solution, which limits the application in water treatment. The new adsorbents requested by the industry should have high capacity, rapid adsorption kinetics and operational stability at elevated temperatures in the presence of steam and other reaction components. The new adsorption processes may then take advantage of such materials.
Polymers could represent good adsorbent candidates displaying a pronounced chemical versatility given by the great number of chemical functionalities or motifs present in their structures. Recently, researchers have focused on the syntheses of zwitterionic cross-linked inorganic and/or organic hybrid polymer materials for the removal of heavy metal ions via electrostatic effects [Liu, J., et al., Novel negatively charged hybrids. 3. Removal of Pb2+ from aqueous solution using zwitterionic hybrid polymers as adsorbent. Journal of Hazardous Materials, 2010. 173(1-3): p. 438-444; Liu, J., et al., Preparation of zwitterionic hybrid polymer and its application for the removal of heavy metal ions from water. Journal of Hazardous Materials, 2010. 178(1-3): p. 1021-1029; Liu, J., et al., Novel negatively charged hybrids. 1. copolymers: Preparation and adsorption properties. Separation and Purification Technology, 2009. 66(1): p. 135-142 (references), each incorporated herein by reference in their entirety]. Considerable attention has been given to synthesize chelating agents containing an amino methyl phosphonate motif owing to its extraordinary chelating properties in extracting heavy metal ions from wastewater. More recently, a porous resin with Schiff base chelating groups for removal of heavy metal ions from aqueous solutions has been synthesized [Ceglowski, M. and G. Schroeder, Preparation of porous resin with Schiff base chelating groups for removal of heavy metal ions from aqueous solutions. Chemical Engineering Journal, 2015. 263(0): p. 402-411 (reference), incorporated herein by reference in its entirety].
In view of the foregoing, there exists a need for novel materials and compositions with high adsorption capacity for Pb2+ and advantageously, a range of other metals, over a short equilibrium time.